Sulfur-containing urethane-based resin and composition and process for producing the resin

ABSTRACT

A polythiol having four or more functional groups, a process for producing the polythiol comprising reacting thiourea with a specific compound, a sulfur-containing urethane-based resin prepared from the polythiol and a lens made of the resin. The resin has a high refractive index, and low dispersion of refractive index, is lightweight, colorless and transparent, has no optical distortion, and has excellent characteristics in weatherability, dye-affinity, heat resistance, impact resistance and machinability.

This application is a divisional of application Ser. No. 08/753,436,filed Nov. 25, 1996, now U.S. Pat. No. 5,837,797, which is a divisionalof application Ser. No. 08/373,083, filed on Jan. 17, 1995, now U.S.Pat. No. 5,608,115.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a novel polythiol and a process forproducing the same, a sulfur-containing urethane-based resin preparedfrom the polythiol and a lens made of the resin.

The polythiol of the present invention finds wide applications in, forexample, raw materials for synthetic resins, crosslinking agents, epoxyresin curing agents, vulcanizing agents, polymerization regulators,metal complex forming agents and biochemical lubricating oil additivesin addition to the above-mentioned raw material for thesulfur-containing urethane-based resin.

2. Description of the Prior Art

There have hitherto been used, for example, polythiols formed by theesterification of polyols such as pentaerythritol and trimethylolpropanewith mercaptocarboxylic acids such as mercaptopropionic acid andthioglycolic acid for the aforementioned applications. Plastic lensesare lighter in weight, less fragile and easier to dye than inorganiclenses, and hence have been increasingly popular for use as opticalelements such as eyeglass lenses and camera lenses.

Resins formed by subjecting diethylene glycol bis(allylcarbonate)(hereinafter referred to as DAC) to radical polymerization have widelybeen used to date for optical elements.

The resins have a variety of features such as excellent impactresistance, light weight, prominent dye-affinity and superbmachinability including cutting ability and polishing ability.

However, lenses made from DAC have a smaller refractive index (n_(D)=1.50) than inorganic lenses (n_(D) =1.52). In order to obtainequivalent optical properties to glass lenses, it is necessary toincrease the center thickness, peripheral thickness and curvature of thelens and hence the lens as a whole becomes unavoidably thick. Therefore,lens-making resins with higher refractive index are desired. As one ofthe lens-making resins giving higher refractive index, there has beenknown a polyurethane-based resin for making plastic lenses, which isobtained by reacting an isocyanate compound with a hydroxyl compoundsuch as diethylene glycol (Japanese Patent Laid-Open No. 136601/1982),with a halogen-containing hydroxyl compound such astetrabromobisphenol-A (Japanese Patent Laid-Open No. 164615/1983), andwith a diphenyl-sulfide-linkage-containing hydroxyl compound (JapanesePatent Laid-Open No. 194401/1985).

Although lenses made of these prior art resins have improved refractiveindices over lenses made from DAC, their refractive indices are stillinsufficient. Moreover, these resins have such defects as poorweather-ability and impact resistance or large specific gravity due tothe presence of a number of halogen atoms or aromatic rings in themolecule for the purpose of improving their refractive indices.

The present inventors have found earlier that an S-alkyl thiocarbamateresin obtained by reacting pentaerythritol tetrakis(2-mercaptoacetate)(hereinafter referred to as PETG) with xylylene diisocyanate(hereinafter referred to as XDi) has a high refractive index, iscolorless and transparent and has excellent mechanical properties andmachinability (Japanese Patent Laid-Open No. 199016/1985).

However, even the S-alkyl thiocarbamate resin had such defects asinsufficient refractive index, thick peripheral thickness and reducedfashonability when the lens was used for strong sizing of visual acuity.

In consequence, the present inventors have made further examinations tofind out a novel compound, 1,2-bis(2-mercaptoethylthio)-3-propanethiol(hereinafter referred to as GST), and found that resins prepared fromGST have higher refractive indices than the resins from PETG and arecolorless, transparent and excellent in dye-affinity so that they aredistinguished as plastic lens materials (Japanese Patent Laid-Open No.270859/1990).

However, the resin formed by reacting GST with XDi, which is mostgenerally used as a raw material of a plastic lens, has a glasstransition temperature of 98° C., and therefore the lens made of theresin is deformed at a common dyeing temperature for plastic lenses of90 to 95° C., which is close to the critical heat-resistant temperatureof the resin. Hence, the lens needs reheating for its restoration, butthis is troublesome.

Consequently, the inventors have made further examinations, and found2-mercaptoethylthio-1,3-propanedithiol (hereinafter referred to as GMT)which gives heat-resistant resins that are not deformed even at thecommon dyeing temperature (90-95° C.) as well as have equivalent opticalproperties to resins made from GST (Japanese Patent Laid-Open No.208950/1993).

However, GMT is a trifunctional thiol and hence, when it is combinedwith a bifunctional isocyanate to produce a resin, a crosslinkedstructure of the resin is formed at the final stage of thepolymerization so that viscosity increase during the polymerization isslow and resin additives such as a plasticizer usually bleed into themolding from a resin-made gasket used for molding plastic lenses, thusimpairing the transparency of the molding. To solve this problem, thepolymerization is carried out at a low temperature for a long time andthen completed at a high temperature by way of example. This casehowever gives a prolonged polymerization time and reduced productivity.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a polythiol compoundwhich provides with improved productivity, a heat-resistant resin thathas equivalent optical properties compared to one prepared from GST orGMT and is not deformed at the ordinary dyeing temperature (90-95° C.).

With such situations in view, the inventors have made examinations tomeet the above-described requirements and, as a result, found that anovel polythiol with four or more functional groups which has thespecific structure of the present invention can solve the foregoingproblems, leading to completion of the present invention.

The present invention provides:

(I) a polythiol having four or more functional groups represented by anyof the following formula (1): ##STR1## wherein R1, R2, R3 and R4 areeach selected from the group consisting of H, --CH₂ SH, CH₂ SCH₂ CH₂ SH,##STR2## provided that where any one of R1, R2, R3 and R4 is H, at leastone of other three radicals represents ##STR3## where any two of R1, R2,R3 and R4 are H, two of others are independently selected from ##STR4##and any three or all of R1, R2, R3 and R4 are not H simultaneously;formula (2):

    (HSCH.sub.2).sub.4-m C(CH.sub.2 SCH.sub.2 CH.sub.2 SH).sub.m(2)

wherein m denotes an integer of 1 to 3; and formula (3): ##STR5##wherein n denotes an integer of 0 to 3; (II) a process for producing thepolythiol having four or more functional groups according to claim 1,which comprises the steps of the preparation of isothiouronium salt byreacting a compound selected from the group consisting of the followingformulae (4), (5) and (6) with thiourea: ##STR6## wherein A1, A2, A3 andA4 are independently selected from the group consisting of H, --CH₂ X,--CH₂ SCH₂ CH₂ X, ##STR7## provided that where any one of A1, A2, A3 andA4 is H, at least one of other three radicals is ##STR8## where any twoof A1, A2, A3 and A4 are H, two of others are independently selectedfrom ##STR9## and any three or all of A1, A2, A3 and A4 are not Hsimultaneously, and Xs denote each an OH group, a chlorine atom, abromine atom, an iodine atom, a methanesulfonyl group, a benzenesulfonylgroup or a p-toluenesulfonyl group;

    (XCH.sub.2).sub.4-m C(CH.sub.2 SCH.sub.2 CH.sub.2 X).sub.m (5)

wherein m is an integer of 1 to 3 and Xs have the same meaning asdefined above; and ##STR10## wherein n is a integer of 0 to 3 and X isas defined as above, and of hydrolyzing the thus obtained isothiouroniumsalt with a based;

(III) a sulfur-containing urethane-based resin composition comprisingthe polythiol having 4 or more functional groups of item (I) and atleast one isocyanate selected from polyisocyanate compounds,polyisothiocyanate compounds and isocyanato-containingpolyisothiocyanate compounds;

(IV) the composition of item (III) wherein the mixing proportion of theisocyanate to the polythiol is from 0.5 to 3.0 in terms of the molarratio of the functional groups (NCO+NCS)/SH;

(V) a process for producing a sulfur-containing urethane-based resinwhich comprises curing the composition of item (III) by heating;

(VI) a sulfur-containing urethane-based resin obtained by the process ofitem (V);

(VII) the process of item (V) wherein the mixing proportion of theisocyanate to the polythiol is from 0.5 to 3.0 in terms of the molarratio of the functional groups (NCO+NCS)/SH;

(VIII) a sulfur-containing urethane-based resin obtained by the processof item (VII);

(IX) a process for preparing a sulfur-containing urethane-based plasticlens which comprises polymerizing the composition of item (III) in amold and then releasing the molding from the mold;

(X) a sulfur-containing urethane-based plastic lens prepared by theprocess of item (IX);

(XI) the process of item (IX) wherein the mixing proportion of theisocyanate to the polythiol is from 0.5 to 3.0 in terms of the molarratio of the functional groups (NCO+NCS)/SH; and

(XII) a sulfur-containing urethane-based plastic lens prepared by theprocess of item (XI).

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows an infrared absorption spectrum of a plastic lens preparedin accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The polythiol having four or more functional groups represented byformula (1) includes the following compounds by way of example.

(where R1=R2=R3=R4) ##STR11## where R2=R3=H ##STR12## where any one ofR1 through R4 is H: ##STR13##

The polythiols represented by formula (2) are exemplified as follows:##STR14##

The polythiols represented by formula (3) are exemplified as follows:##STR15##

The sulfur-containing urethane-based, resin prepared from the polythiolhaving four or more functional groups according to the present inventionhas solved the above-mentioned problems, and therefore it is colorlessand transparent, shows no optical distortion, has a high refractiveindex and low dispersion of refractive index (a high Abbe's number), isof a low specific gravity, is excellent in impact strength,dye-affinity, heat resistance and machinability, so that it hassatisfactory properties as a resin for plastic lenses.

The polythiol having four or more functional groups according to thepresent invention can be prepared by any known procedure forsynthesizing polythiols as described in literature (e.g. The Chemistryof the Thiol Group), but it is preferable from the aspect of colorationof the product to produce it by the isothiouronium salt process whichcomprises reacting a compound of formula (4), (5) or (6) with thioureato form an isothiouronium salt and hydrolyzing the salt.

The polyols, polyhalogen compounds and hydroxylated halides of formulae(4), (5), and (6) can be obtained, for example, by reacting an organiclow-molecular epoxy compound such as an epihalohydrin and butadieneepoxide, a glycerol derivative such as 2-chloro-1,3-propanediol,thioglycerol and tribromopropane or an organic low-molecular halide suchas 1,2,3,4-tetrabromobutane and 1,2,3,4,5-pentachloropentane with anethylene derivative such as 2-mercaptoethanol and ethylene oxide and asulfide such as sodium hydrogensulfide, sodium sulfide, potassiumsulfide and hydrogen sulfide.

The eliminable-group-containing compounds of formulae (4), (5) and (6)can also be obtained by replacing the OH group or groups of thecorresponding polyol or hydroxylated halide of formula (4), (5) or (6)with the eliminable group or groups.

To replace the OH group or groups with the eliminatable group or groups,it is possible to use reactions for introducing the eliminatable groupor groups into a common alcohol. For example, it is mentioned to reactan alcohol with a hydrogen halide such as hydrogen chloride, hydrobromicacid and hydroiodic acid, to use in the reactions the hydrogen halideand a metal halide such as zinc chloride, to use an alkali metal saltsuch as potassium iodide and sodium bromide and an acid such as sulfuricacid and phosphoric acid, to use a halogen and phosphorus, and to usethionyl chloride, phosphorus tribromide, phosphorus pentachloride,methanesulfonyl chloride, benzenesulfonyl chloride, p-toluenesulfonylchloride, or the like.

In the next step of the isothiouronium salt reaction, a polyfunctionalcompound of formula (4), (5) or (6) is reacted with generally fourequivalents or more, preferably four to eight equivalents of thioureabased on the compound. Where the compound contains an OH group orgroups, the reaction is effected in the presence of generally oneequivalent or more, preferably one to five equivalents of a mineral acidbased on the OH group or groups. The mineral acid includes hydrochloricacid, hydrobromic acid, hydroiodic acid, sulfuric acid, phosphoric acid,etc., but hydrochloric acid or hydrobromic acid is preferred from theviewpoint of reaction rate, economical efficiency and coloring of theproduct.

The subsequent hydrolysis is carried out by adding to the foregoingreaction liquid generally four equivalents or more, preferably four totwenty equivalents of an inorganic base such as sodium hydroxide,potassium hydroxide, sodium carbonate, sodium acetate and potassiumphosphate or an organic base such as ammonia, triethylamine andhydrazine based on the polyfunctional compound of formula (4), (5) or(6) to obtain a desired polythiol having four or more functional groups.

No limitations are imposed on the reaction temperatures up to theobtainment of the polythiol having four or more functional groups,because they vary with the processes and catalysts employed. However,the reaction for obtaining the compound of formula (4), (5) or (6), theisothiouronium salt reaction and the hydrolysis are all carried outpreferably at 0 to 200° C., more preferably at 20 to 120° C. by way ofexample.

Similarly, the reaction pressure is not limited and therefore reduced,atmospheric or elevated pressure may be employed. However, atmosphericpressure is preferred because of cost and reduction of equipment andfacility.

The polythiol having four or more functional groups of formula (1), (2)or (3) obtained in the above manner can be purified by common proceduresincluding acid washing, base washing, water washing, concentration,filtration, etc. and can also be distilled, if necessary, after it hasbeen extracted with an organic solvent such as toluene. The preparationof the polythiol having four or more functional groups can be effectedin the air, but it is preferable to carry out the preparation as a wholein a stream of nitrogen in order to make assurance in the prevention ofoxidation and coloring of the raw materials and the product.

The synthesis of the polythiol having four or more functional groupsaccording to the present invention is illustrated below. For example,where R1=R3=H and R2=R4= ##STR16## in formula (1), the polythiol can besynthesized in the following manner: ##STR17##

Namely, epichlorohydrin is reacted with 2-mercaptoethanol in thepresence of triethylamine to obtain a diol, which is further reactedwith sodium sulfide to obtain a tetraol.

The tetraol is reacted with thiourea in hydrochloric acid to obtain anisothiouronium salt. At this moment, rearrangement takes place to forman isomer mixture tetraisothiouronium salt containing that of formula(7).

Finally, aqueous ammonia is added to the reaction liquid to hydrolyzethe salt so as to obtain an isomer mixture polythiol containing thedesired polythiol of formula (8).

As another method, where R1=R2=R3=R4=--CH₂ SH in formula (1) by way ofexample, the polythiol can be synthesized also in the following manner:##STR18##

Namely, epichlorohydrin is reacted with thioglycerol in the presence oftriethylamine to obtain a triol.

Then, the reaction liquid is reacted with thionyl chloride to obtain achlorinated derivative. At this moment, rearrangement takes placepartially to form an isomer mixture tetrachloride-containing that offormula (9). Then, the isomer mixture tetrachloride is reacted withthiourea to form an isothiouronium salt, to which hydrazine hydrate isadded to hydrolyze the salt to obtain the desired polythiol of formula(10). The rearrangement is completed by the isothiouronium saltreaction.

The sulfur-containing urethane-based resin of the present invention isobtained by reacting a polythiol of formulae (1) through (3) with atleast one isocyanate selected from polyisocyanate compounds,polyisothiocyanate compounds and isocyanato-containingpolyisothiocyanates.

Active hydrogen compounds such as hydroxyl compounds, mercapto compoundsother than those of formulae (1) to (3) and hydroxylated mercaptocompounds or monoisocyanates such as monoisocyanate compounds andmonoisothiocyanate compounds may be added to the reaction system inorder to modify the resin.

The polyisocyanate compound used as a raw material for thesulfur-containing urethane-based resin in the present inventionincludes, for example, aliphatic polyisocyanates such as ethylenediisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate,hexamethylene diisocyanate, octamethylene diisocyanate, nonamethylenediisocyanate, 2,2'-dimethylpentane diisocyanate, 2,2,4-trimethylhexanediisocyanate, decamethylene diisocyanate, butene diisocyanate,1,3-butadiene-1,4-diisocyanate, 2,4,4-trimethylhexamethylenediisocyanate, 1,6,11-undecatriisocyanate, 1,3,6-hexamethylenetriisocyanate, 1,8-diisocyanato-4-(isocyanatomethyl)octane,2,5,7-trimethyl-1,8-diisocyanato-5-(isocyanatomethyl)octane,bis(isocyanatoethyl)-carbonate, bis(isocyanatoethyl)ether,1,4-butyleneglycol-dipropylether-ω,ω'-diisocyanate, lysinediisocyanatemethyl ester, lysinetriisocyanate,2-isocyanatoethyl-2,6-diisocyanatohexanoate,2-isocyanatopropyl-2,6-diisocyanatohexanoate, xylylene diisocyanate,bis(isocyanatoethyl)benzene, bis-(isocyanatopropyl)benzene,α,α,α',α'-tetramethylxylylene diisocyanate, bis(isocyanatobutyl)benzene,bis(isocyanatomethyl)naphthalene, bis(isocyanatomethyl)diphenyl ether,bis(isocyanatoethyl)phthalate, mesitylene triisocyanate and2,6-di(isocyanatomethyl)furan; alicyclic polyisocyanates such asisophorone diisocyanate, bis(isocyanatomethyl)cyclohexane,dicyclohexylmethane diisocyanate, cyclohexane diisocyanate,methylcyclohexane diisocyanate, dicyclohexyldimethylmethanediisocyanate, 2,2'-dimethyldicyclohexylmethane diisocyanate,bis(4-isocyanato-n-butylidene)pentaerythritol, dimeric aciddiisocyanate,2-isocyanatomethyl-3-(3-isocyanatopropyl)-5-isocyanatomethyl-bicyclo[2.2.1]-heptane,2-isocyanatomethyl-3-(3-isocyanatopropyl)-6-isocyanatomethyl-bicyclo[2.2.1]-heptane,2-isocyanatomethyl-2-(3-isocyanatopropyl)-5-isocyanatomethyl-bicyclo[2.2.1]-heptane,2-isocyanatomethyl-2-(3-isocyanatopropyl)-6-isocyanatomethyl-bicyclo[2.2.1]-heptane,2-isocyanatomethyl-3-(3-isocyanatopropyl)-6-(2-isocyanatoethyl)-bicyclo[2.2.1]-heptane,2-isocyanatomethyl-3-(3-isocyanatopropyl)-6-(2-isocyanatoethyl)-bicyclo[2.1.1]-heptane,2-isocyanatomethyl-2-(3-isocyanatopropyl)-5-(2-isocyanatoethyl)-bicyclo[2.2.1]-heptane,and2-isocyanatomethyl-2-(3-isocyanatopropyl)-6-(2-isocyanatoethyl)-bicyclo[2.2.1]-heptane;

aromatic polyisocyanates such as phenylene diisocyanate, tolylenediisocyanate, ethylphenylene diisocyanate, isopropylphenylenediisocyanate, dimethylphenylene diisocyanate, diethylphenylenediisocyanate, diisopropylphenylene diisocyanate, trimethylbenzenetriisocyanate, benzene triisocyanate, naphthalene diisocyanate,methylnaphthalene diisocyanate, biphenyl diisocyanate, tolidinediisocyanate, 4,4'-diphenylmethane diisocyanate,3,3'-dimethyl-diphenylmethane-4,4'-diisocyanate,bibenzyl-4,4'-diisocyanate, bis(isocyanatophenyl)ethylene,3,3'-dimethoxybiphenyl-4,4'-diisocyanate, triphenylmethanetriisocyanate, polymeric MDI, naphthalene triisocyanate,diphenylmethane-2,4,4'-triisocyanate,3-methyldiphenylmethane-4,6,4'-triisocyanate,4-methyldiphenyl-methane-3,5,2',4',6'-pentaisocyanate,phenylisocyanatomethyl isocyanate, phenylisocyanatoethyl isocyanate,tetrahydronaphthylene diisocyanate, hexahydrobenzene diisocyanate,hexahydrodiphenylmethane-4,4'-diisocyanate, diphenylether diisocyanate,ethyleneglycol-diphenylether diisocyanate,1,3-propyleneglycoldiphenylether diisocyanate, benzophenonediisocyanate, diethyleneglycol-diphenylether diisocyanate, dibenzofurandiisocyanate, carbazole diisocyanate, ethylcarbazole diisocyanate anddichlorocarbazole diisocyanate;

sulfur-containing aliphatic polyisocyanates such as thiodiethyldiisocyanate, thiodipropyl diisocyanate, thiodihexyl diisocyanate,dimethylsulfone diisocyanate, dithiodimethyl diisocyanate, dithiodiethyldiisocyanate, dithiodipropyl diisocyanate anddicyclohexylsulfide-4,4'-diisocyanate;

aromatic sulfide-type polyisocyanates such asdiphenylsulfide-2,4'-diisocyanate, diphenylsulfide-4,4'-diisocyanate,3,3'-dimethoxy-4,4'-diisocyanatodibenzyl thioether,bis(4-isocyanatomethylbenzene)-sulfide and4,4'-methoxybenzene-thioethyleneglycol-3,3'-diisocyanate;

aromatic disulfide-type polyisocyanates such asdipenyldisulfide-4,4'-diisocyanate,2,2'-dimethyldiphenyl-disulfide-5,5'-diisocyanate,3,3'-dimethyldiphenyldisulfide-5,5'-diisocyanate,3,3'-dimethyldiphenyldisulfide-6,6'-diisocyanate,4,4'-dimethyldiphenyldisulfide-5,5'-diisocyanate,3,3'-dimethoxydiphenyldisulfide-4,4'-diisocyanate and4,4'-dimethoxydiphenyldisulfide-3,3'-diisocyanate;

aromatic sulfone-type polyisocyanates such asdiphenylsulfone-4,4'-diisocyanate, diphenylsulfone-3,3'-diisocyanate,benzidinesulfone-4,4'-diusocyanate,diphenylmethanesulfone-4,4'-diisocyanate,4-methyldiphenylmethanesulfone-2,4'-diisocyanate,4,4'-dimethoxydiphenylsulfone-3,3'-diisocyanate,3,3'-dimethoxy-4,4'-diisocyanatodibenzylsulfone,4,4'-dimethyldiphenylsulfone-3,3'-diisocyanate,4,4'-di-tert-butyl-diphenylsulfone-3,3'-diisocyanate,4,4'-methoxybenzene ethylenedisulfone-3,3'-diisocyanate and4,4'-dichlorodiphenylsulfone-3,3'-diisocyanate;

sulfonic ester-type polyisocyanates such as4-methyl-3-isocyanatobenzenesulfonyl-4'-isocyanato-phenol ester,4-methoxy-3-isocyanatobenzenesulfonyl-4'-isocyanato-phenol ester;

aromatic sulfonic amides such as4-methyl-3-isocyanatobenzene-sulfonylanilide-3'-methyl-4'-isocyanate,dibenzenesulfonyl-ethylenediamine-4,4'-diisocyanate,4,4'-methoxybenzenesulfonyl-ethylenediamine-3,3'-diisocyanate and4-methyl-3-isocyanatobenzene-sulfonylanilide-4-methyl-3'-isocyanate; and

sulfur-containing heterocyclic compounds such asthiophene-2,5-diisocyanate, thiophene-2,5-diisocyanatomethyl and1,4-dithian-2,5-diisocyanate.

Halogenated derivatives such as chlorinated and brominated derivatives,alkylated derivatives, alkoxylated derivatives, nitrated derivatives,prepolymer type addition products with polyhydric alcohols, carbodiimidemodified derivatives, urea modified derivatives, biuret modifiedderivatives and dimerization or trimerization products of thesepolyisocyanate compounds may also be used in the present invention.

The polyisothiocyanate compound used as a raw material in the presentinvention has two or more --NCS groups in the molecule and may alsocontain sulfur atom or atoms in addition to the isothiocyanate groups.

The polyisothiocyanate compound includes, for example, aliphaticpolyisothiocyanates such as 1,2-diisothiocyanatoethane,1,3-diisothiocyanatopropane, 1,4-diisothiocyanatobutane,1,6-diisothiocyanatohexane and p-phenylenediisopropylidenediisothiocyanate;

alicyclic polyisothiocyanates such as cyclohexane diisothiocyanate;

aromatic polyisothiocyanates such as 1,2-diisothiocyanatobenzene,1,3-diisothiocyanatobenzene, 1,4-diisothiocyanatobenzene,2,4-diisothiocyanatotoluene, 2,5-diisothiocyanato-m-xylene,4,4'-diisothiocyanato-1,1'-biphenyl,1,1'-methylenebis(4-isothiocyanatobenzene),1,1'-methylenebis(4-isothiocyanato-2-methylbenzene),1,1'-methylenebis(4-isothiocyanato-3-methylbenzene),1,1'-(1,2-ethane-diyl)bis(4-isothiocyanatobenzene),4,4'-diisothiocyanatobenzophenone,4,4'-diiso-thiocyanato-3,3'-dimethylbenzophenone,benzanilide-3,4'-diisothiocyanate, diphenylether-4,4'-diisothiocyanateand diphenylamine-4,4'-diisothiocyanate;

heterocyclic polyisothiocyanates such as2,4,6-triisothiocyanato-1,3,5-triazine; and

carbonyl polyisothiocyanates such as hexane-dioyl diisothiocyanate,nonanedioyl diisothiocyanate, carbonic diisothiocyanate,1,3-benzenedicarbonyl diisothiocyanate, 1,4-benzenedicarbonyldiisothiocyanate and (2,2'-bipyridine)-4,4'-dicarbonyl diisothiocyanate.

The polyisothiocyanate having one or more sulfur atoms in addition tothe isothiocyanate groups and two or more functional groups used as araw material in the present invention includes, for example,sulfur-containing aliphatic polyisothiocyanates such asthiobis(3-isothiocyanatopropane), thiobis(2-isothiocyanatoethane) anddithiobis(2-isothiocyanato-ethane);

sulfur-containing aromatic polyisothiocyanates such as1-isothiocyanato-4-[(2-isothiocyanato)sulfonyl]benzene,thiobis(4-isothiocyanatobenzene), sulfonylbis(4-isothiocyanatobenzene),sulfinylbis(4-isothiocyanatobenzene),dithiobis(4-isothio-cyanatobenzene),4isothiocyanato-1-[(4-isothiocyanatophenyl)-sulfonyl]-2-methoxybenzene,4-methyl-3-isothiocyanatobenzene-sulfony-4'-isothiocyanate phenyl esterand4-methyl-3-isothiocyanatobenzene-sulfonylanilide-3'-methyl-4'-isothiocyanate;and

sulfur-containing heterocyclic compounds such asthiophene-2,5-diisothiocyanate and 1,4-dithian-2,5-diisothiocyanate.

Further, halogenated derivatives such as chlorinated and brominatedderivatives, alkylated derivatives, alkoxylated derivatives, nitratedderivatives, prepolymer type addition products with polyhydric alcohols,carbodiimide modified derivatives, urea modified derivatives, biuretmodified derivatives and dimerization and trimerization products ofthese polyisothiocyanate compounds may also be used in the presentinvention.

The isocyanato-containing polyisothiocyanate compound used as a rawmaterial in the present invention includes, for example, aliphatic andalicyclic compounds such as 1-isothiocyanato-3-isocyanatopropane,1-isothiocyanato-5-isocyanatopentane,1-isothiocyanato-6-isocyanatohexane, isothiocyanatocarbonyl isocyanateand 1-isothiocyanato-4-isocyanatocylohexane;

aromatic compounds such as 1-isothiocyanato-4-isocyanatobenzene and4-methyl-3-isothiocyanato-1-isozcyanatobenzene;

heterocyclic compounds such as2-isocyanato-4,5-diisothiocyanato-1,3,5-triazine; and

compounds having sulfur atoms in addition to isothiocyanate groups suchas 4-isocyanato-4'-isothiocyanatodiphenyl sulfide and2-isocyanato-2'-isothiocyanatodiethyl disulfide.

Further, halogenated derivatives such as chlorinated and brominatedderivatives, alkylated derivatives, alkoxylated derivatives, nitratedderivatives, prepolymer type addition products with polyhydric alcohols,carbodilmide modified derivatives, urea modified derivatives, biuretmodified derivatives and dimerization or trimerization products of thesecompounds may also be used in the present invention.

These isocyanates may be used singly or as a mixture of two or more ofthem.

The active hydrogen compound used as a modifier of the sulfur-containingurethane-based resin of the present invention is selected from hydroxylcompounds, mercapto compounds and hydroxylated mercapto compounds.

The hydroxyl compounds include, for example, methanol, benzyl alcohol,phenol, ethoxy ethanol;

aliphatic polyols such as ethylene glycol, diethylene glycol, propyleneglycol, dipropylene glycol, butylene glycol, neopentyl glycol, glycerol,trimethylolethane, trimethylolpropane, butanetriol, 1,2-methylglucoside,pentaerythritol, dipentaerythritol, tripentaerythritol, sorbitol,erythritol, threitol, ribitol, arabinitol, xylitol, allitol, mannitol,dulcitol, iditol, glycol, inositol, hexanetriol, triglycerol,diglycerol, triethylene glycol, polyethylene glycol,tris(2-hydroxyethyl)-isocyanurate, cyclo-butanediol, cyclopentanediol,cyclohexanediol, cycloheptanediol, cyclooctanediol,cyclohexanedimethanol, hydroxypropyl-cyclohexanol,tricyclo[5,2,1,0,2,6]-decanedimethanol, bicyclo[4,3,0]nonanediol,dicyclohexanediol, tricyclo[5.3.1.1]dodecanediol,bicyclo[4.3.0]-nonane-dimethanol, tricyclo[5.3.1.1]-dodecane-diethanol,hydroxypropyl-tricyclo[5.3.1.1]dodecanol, spiro[3.4]-octanediol,butylcyclohexanediol, 1,1'-bicyclohexylidenediol, cyclohexanetriol,maltitol and lactitol;

aromatic polyols such as dihyroxynaphthalene trihydroxynaphthalene,tetrahydroxynaphthalene, dihydroxybenzene, benzenetriol,biphenyltetraol, pyrogallol, (hydroxynaphthyl)-pyrogallol,trihydroxyphenanthrene, bisphenol-A, bisphenol-F, xylyleneglycol,di(2-hydroxyethoxy)benzene, bisphenol-A-bis(2-hydroxyethylether),tetrabromobisphenol-A andtetrabromobisphenol-A-bis(2-hydroxyethylether);

halogenated polyols such as dibromoneopentylglycol;

high molecular polyols such as epoxy resin;

condensed products of the above-mentioned polyols with organic acidssuch as oxalic acid, glutamic acid, adipic acid, acetic acid, propionicacid, cyclohexanecarboxylic acid, β-oxo-cyclohexanepropionic acid, dimeracid, phthalic acid, isophthalic acid, salicylic acid, 3-bromopropionicacid, 2-bromoglycolic acid, cyclohexanedicarboxylic acid, pyromelliticacid, butanetetracarboxylic acid and bromophthalic acid;

addition products of alkylene oxides such as ethylene oxide andpropylene oxide to the above polyols and to alkylenepolyamines; and

sulfur-containing polyols such as bis[4-(hydroxyethoxy) phenyl] sulfide,bis[4-(2-hydroxypropoxy)phenyl] sulfide,bis[4-(2,3-dihydroxypropoxy)phenyl] sulfide,bis[4-(4-hydroxycyclohexyloxy)-phenyl] sulfide,bis[2-methyl-4-(hydroxyethoxy)-6-butylphenyl] sulfide, compoundsobtained by the addition of ethylene oxide and/or propylene oxide to thesulfur-containing polyols in an amount of not more than 3 moles onaverage per mole of hydroxyl group of the polyols, di(2-hydroxyethyl)sulfide, 1,2-bis(2-hydroxyethylmercapto)ethane, bis(2-hydroxyethyl)disulfide, 1,4-dithian-2,5-diol, bis(2,3-dihydroxypropyl) sulfide,tetrakis(4-hydroxy-2-thiabutyl)methane, bis(4-hydroxyphenyl) sulfone(trade name : Bisphenol-S), tetrabromobisphenol-S,tetramethylbisphenol-S, 4,4'-thiobis(6-tert-butyl-3-methylphenol) and1,3-bis(2-hydroxyethylthioethyl)cyclohexane.

The mercapto compounds include, for example, methyl mercaptan,benzenethiol, benzylthiol; aliphatic polythiols such as methanedithiol,1,2-ethanedithiol, 1,1-propanedithiol, 1,2-propanedithiol,1,3-propanedithiol, 2,2-propanedithiol, 1,6-hexanedithiol,1,2,3-propanetrithiol, tetrakis(mercaptomethyl)-methane,1,1-cyclohexanedithiol, 1,2-cyclohexanedithiol,2,2-dimethylpropane-1,3-dithiol, 3,4-dimethoxybutane-1,2-dithiol,2-methylcyclohexane-2,3-dithiol,bicyclo[2.2.1]hepta-exo-cis-2,3-dithiol, 1,1-bis(mercaptomethyl)cyclohexane, thiomalic acid bis(2-mercaptoethyl ester),2,3-dimercaptosuccinic acid (2-mercapto-ethyl ester),2,3-dimercapto-1-propanol (2-mercaptoacetate), 2,3-dimercapto-1-propanol(3-mercaptoacetate), diethylene glycol bis(2-mercaptoacetate),diethylene glycol bis(3-mercapto-propionate), 1,2-dimercaptopropylmethyl ether, 2,3-dimercaptopropyl methyl ether,2,2-bis(mercaptomethyl)-1,3-propanedithiol, bis(2-mercaptoethyl) ether,ethylene glycol bis(2-mercapto-acetate), ethylene glycolbis(3-mercaptopropionate), trimethylol-propane tris(2-mercaptoacetate),trimethylolpropane tris(3-mercaptopropionate), pentaerythritoltetrakis(2-mercaptoacetate), pentaerythritoltetrakis(3-mercaptopropionate) and1,2-bis(2-mercaptoethylthio)-3-mercaptopropane;

aromatic polythiols such as 1,2-dimercaptobenzene,1,3-dimercaptobenzene, 1,4-dimercaptobenzene,1,2-bis(mercaptomethyl)benzene, 1,3-bis(mercaptomethyl)benzene1,4-bis(mercaptomethyl)benzene, 1,2-bis(mercaptoethyl)benzene,1,3-bis(mercaptoethyl)benzene, 1,4-bis(mercaptoethly)benzene,1,2-bis(mercaptomethyleneoxy)benzene,1,3-bis(mercaptomethyleneoxy)benzene,1,4-bis(mercaptomethyleneoxy)benzene,1,2-bis(mercaptoethyleneoxy)benzene,1,3-bis(mercaptoethyleneoxy)benzene,1,4-bis(mercaptoethyleneoxy)benzene, 1,2,3-trimercaptobenzene,1,2,4-trimercaptobenzene, 1,3,5-trimercaptobenzene,1,2,3-tris(mercaptomethyl)benzene, 1,2,4-tris(mercaptomethyl) benzene,1,3,5-tris(mercaptomethyl)benzene, 1,2,3-tris(mercaptoethyl)benzene,1,2,4-tris(mercaptoethyl)benzene, 1,3,5-tris(mercaptoethyl)benzene,1,2,3-tris(mercaptomethyleneoxy)benzene,1,2,4-tris(mercaptomethyleneoxy)benzene,1,3,5-tris(mercaptomethyleneoxy)benzene,1,2,3-tris(mercapto-ethyleneoxy)benzene,1,2,4-tris(mercaptoethyleneoxy)benzene,1,3,5-tris(mercaptoethyleneoxy)benzene, 1,2,3,4-tetramercaptobenzene,1,2,3,5-tetramercaptobenzene, 1,2,4,5-tetramercaptobenzene,1,2,3,4-tetrakis(mercaptomethyl)benzene,1,2,3,5-tetrakis(mercaptomethyl)benzene,1,2,4,5-tetrakis(mercaptomethyl)benzene,1,2,3,4-tetrakis(mercaptoethyl)benzene,1,2,3,5-tetrakis(mercaptoethyl)benzene,1,2,4,5-tetrakis(mercaptoethyl)benzene,1,2,3,4-tetrakis(mercaptomethyleneoxy)benzene,1,2,3,5-tetrakis(mercaptomethyleneoxy)benzene,1,2,4,5-tetrakis(mercaptomethyleneoxy)benzene,1,2,3,4-tetrkis(mercapto-ethyleneoxy)benzene,1,2,3,5-tetrakis(mercaptoethyleneoxy)benzene,1,2,4,5-tetrakis(mercaptoethyleneoxy)benzene, 2,2'-dimercaptobiphenyl,4,4'-dimercaptobiphenyl, 4,4'-dimercaptobibenzyl, 2,5-toluenedithiol,3,4-toluenedithiol, 1,4-naphthalenedithiol, 1,5-naphthalenedithiol,2,6-naphthalenedithiol, 2,7-naphthalenedithiol,2,4-dimethylbenzene-1,3-dithiol, 4,5-dimethylbenzene-1,3-dithiol,9,10-anthracene-dimethanethiol,1,3-di(p-methoxyphenyl)propane-2,2-dithiol,1,3-diphenylpropane-2,2-dithiol, phenylmethane-1,1-dithiol and2,4-di(p-mercaptophenyl)pentane;

halogenated aromatic polythiols including chlorinated or brominatedpolythiols such as 2,5-dichlorobenzene-1,3-dithiol,1,3-di(p-chlorophenyl)propane-2,2-dithiol,3,4,5-tribromo-1,2-dimercaptobenzene and2,3,4,6-tetrachloro-1,5-bis(mercaptomethyl)benzene; heterocyclicpolythiols such as 2-methylamino-4,6-dithiol-sym-triazine,2-ethylamino-4,6-dithiol-sym-triazine, 2-amino-4,6-dithiol-sym-triazine,2-morphorino-4,6-dithiol-sym-triazine,2-cyclohexyl-amino-4,6-dithiol-sym-triazine,2-methoxy-4,6-dithiol-sym-triazine, 2-phenoxy-4,6-dithiol-sym-triazine,2-thiobenzeneoxy-4,6-dithiol-sym-triazine and2-thiobutyloxy-4,6-dithiol-sym-triazine;

aromatic polythiols containing sulfur atoms in addition to mercaptogroups such as 1,2-bis(mercaptomethylthio)benzene,1,3-bis(mercaptomethylthio)benzene, 1,4-bis(mercaptomethylthio)benzene,1,2-bis(mercaptoethylthio)benzene, 1,3-bis(mercaptoethylthio)benzene,1,4-bis(mercaptoethylthio)benzene,1,2,3-tris(mercaptomethylthio)benzene,1,2,4-tris(mercaptomethylthio)benzene,1,3,5-tris(mercaptomethylthio)benzene,1,2,3-tris(mercaptoethylthio)benzene,1,2,4-tris(mercaptoethylthio)benzene,1,3,5-tris(mercaptoethylthio)benzene,1,2,3,4-tetrakis(mercaptomethylthio)benzene,1,2,3,5-tetrakis(mercapto-methylthio) benzene,1,2,4,5-tetrakis(mercaptomethylthio)benzene,1,2,3,4-tetrakis(mercaptoethylthio)benzene,1,2,3,5-tetrakis(mercaptoethylthio)benzene,1,2,4,5-tetrakis(mercaptoethylthio)benzene and aromatic ring alkylatedderivatives of these polythiols;

aliphatic polythiols containing sulfur atoms in addition to mercaptogroups such as bis(mercaptomethyl) sulfide, bis(mercaptoethyl) sulfide,bis(mercaptopropyl) sulfide, bis(mercaptomethylthio)methane,bis(2-mercaptoethylthio) methane, bis(3-mercaptopropylthio)methane,1,2-bis(mercaptomethylthio) ethane, 1,2-bis(2-mercaptoethylthio)ethane,1,2-bis(3-mercaptopropylthio)ethane, 1,3-bis(mercaptomethylthio)propane,1,3-bis(2-mercaptoethylthio)propane,1,3-bis(3-mercaptopropylthio)propane,1,2-bis(2-mercaptoethylthio)-3-mercaptopropane,2-mercaptoethylthio-1,3-propanedithiol,1,2,3-tris(mercaptomethylthio)propane,1,2,3-tris(2-mercaptoethylthio)propane,1,2,3-tris(3-mercaptopropylthio)propane,tetrakis(mercaptomethylthiomethyl)methane,tetrkis(2-mercaptoethylthiomethyl)methane,tetrakis(3-mercaptopropylthiomethyl) methane, bis(2,3-dimercaptopropyl)sulfide, 2,5-dimercapto-1,4-dithian, bis(mercaptomethyl) disulfide,bis(mercaptoethyl) disulfide and bis(mercaptopropyl) disulfide; estersof mercaptoacetic acid and mercaptopropionic acid with these compounds;

aliphatic polythiols containing sulfur atoms in addition to mercaptogroups such as hydroxymethyl sulfide bis(2-mercaptoacetate),hydroxymethyl sulfide bis(3-mercaptopropionate), hydroxyethyl sulfidebis(2-mercaptoacetate), hydroxyethyl sulfide bis(3-mercaptopropionate),hydroxypropyl sulfide bis(2-mercaptoacetate), hydroxypropyl sulfidebis(3-mercaptopropionate), hydroxymethyl disulfidebis(2-mercaptoacetate), hydroxymethyl disulfidebis(3-mercaptopropionate), hydroxyethyl disulfidebis(2-mercaptoacetate), hydroxyethyl disulfidebis(3-mercaptopropionate), hydroxypropyl disulfidebis(2-mercaptoacetate), hydroxypropyl disulfidebis(3-mercaptopropionate), 2-mercaptoethyl ether bis(2-mercaptoacetate),2-mercaptoethyl ether bis(3-mercaptopropionate), 1,4-dithian-2,5-diolbis(2-mercaptoacetate), 1,4-dithian-2,5-diol bis(3-mercaptopropionate),thioglycolic acid bis(2-mercaptoethyl ester), thiodipropionic acidbis(2-mercaptoethyl ester), 4,4-thiodibutyric acid bis(2-mercaptoethylester), dithiodiglycolic acid bis(2-mercaptoethyl ester),dithiodipropionic acid bis(2-mercaptoethyl ester), 4,4-dithiodibutyricacid bis(2-mercaptoethyl ester), thiodiglycolic acidbis(2,3-dimercaptopropyl ester), thiodipropionic acidbis(2,3-dimercaptopropyl ester), dithiodiglycolic acidbis(2,3-dimercaptopropyl ester) and dithiodipropionic acidbis(2,3-dimercaptopropyl ester); and

heterocyclic compounds containing sulfur atoms in addition to mercaptogroups such as 3,4-thiophene-dithiol , 2,5-dimercapto-1,3,4-thiadiazol,2,5-dimercapto-1,4-dithan and 2,5-dimercaptomethyl-1,4-dithian.

The hydroxylated mercapto compound includes, for example,2-mercaptoethanol, 3-mercapto-1,2-propanediol, glyceroldi(mercaptoacetate), 1-hydroxy-4-mercaptocyclohexane,2,4-dimercaptophenol, 2-mercaptohydroquinone, 4-mercaptophenol,1,3-dimercapto-2-propanol, 2,3-dimercapto-1-propanol,1,2-dimercapto-1,3-butanediol, pentaerythritoltris(3-mercaptopropionate), pentaerythritol mono(3-mercaptopropionate),pentaerythritol bis(3-mercaptopropionate), pentaerythritoltris(thioglycolate), pentaerythritol pentakis(3-mercaptopropionate),hydroxymethyltris(mercaptoethylthiomethyl)methane,1-hydroxyethylthio-3-mercaptoethylthiobenzene,4-hydroxy-4'-mercaptodiphenyl sulfone, 2-(2-mercaptoethylthio)ethanol,dihydroxyethyl sulfide mono(3-mercaptopropionate), dimercaptoethanemonosalicylate andhydroxyethylthiomethyl-tris(nercaptoethylthio)methane.

Further, halogenated derivatives such as chlorinated and brominatedderivatives of the active hydrogen compounds may also be used in thepresent invention. They may be used singly or as a mixture of two ormore of them.

The monocyanate used as a modifier of the sulfurcontainingurethane-based resin of the present invention is selected frommonoisocyanate compounds and monoisothiocyanate compounds.

The monoisocyanate compounds include, for example, phenyl isocyanate,butyl isocyanate, cyclohexyl isocyanate, etc.

The monoisothiocyanate compounds include, for example, phenylisothiocyanate, butyl isothiocyanate, cyclohexyl isothiocyanate, etc.

Halogenated derivatives such as chlorinated or brominated derivatives,alkylated derivatives, alkoxylated derivatives and nitrated derivativesof these compounds may also be used. They may be used singly or as amixture of two or more of them.

The proportion of at least one isocyanate selected from thepolyisocyanate compounds, polyisothiocyanate compounds andisocyanato-containing polyisothiocyanate compounds to the polythiol isgenerally 0.5 to 3.0, preferably 0.5 to 1.5 in terms of the molar ratioof the functional groups (NCO+NCS)/SH.

The plastic lens of the present invention is made of an S-alkylthiocarbamate resin or a dithiourethane resin. The resins are primarilycomposed respectively of S-alkyl thiocarbamate bonds formed by reactingisocyanate groups with mercapto groups and dithiourethane bonds formedby reacting isothiocyanate groups with mercapto groups. The resins mayalso contain allophanate bonds, urea bonds, thiourea bonds, biuretbonds, etc. in addition to the above described bonds for desiredpurposes.

For example, when S-alkyl thiocarbamate bonds are additionally reactedwith isocyanate groups or dithiourethane bonds are further reacted withisothiocyanate groups to increase crosslinking density, favorableresults are often obtained. In such reactions, the temperature should beraised to at least 100° C. and the amount of the isocyanate orisothiocyanate component should be increased. Further, an amine or thelike may be used partially in combination to form urea bonds or biuretbonds. However, particular attention should be paid to the coloring ofthe resin and/or lens when a compound other than the active hydrogencompound is reacted with the isocyanate compound or isothiocyanatecompound in the above manner.

A variety of agents such as an internal mold releasing agent, chainextender, crosslinking agent, light stabilizer, ultraviolet absorber,antioxidant, oil soluble dye and filler may be added to the resin inaccordance with purposes in the same manner as in the molding processesknown in the art.

To control the reaction rate at a desired value, it is also possible toadd properly known reaction catalysts used in the production ofpolyurethane.

The lens of the present invention is generally prepared by a castingpolymerization process. Specifically, a polyisocyanate is mixed with apolythiol having 4 or more functional groups represented by formulae (1)to (3). The mixture is deaerated by a suitable means, if necessary, andthen poured into a mold where it is polymerized generally by increasingthe temperature slowly from a low temperature of about 0 to 5° C. to ahigh temperature of about 100 to 180° C. Here, a known mold releasingtreatment may be applied to the mold in advance to facilitate moldreleasing after the polymerization.

The thus-obtained sulfur-containing urethane-based resin according tothe present invention is of extremely low dispersion of refractiveindex, has a high refractive index, is excellent in heat resistance andcolorless and transparent, has no optical distortion, is lightweight andhas excellent characteristics in weatherability, dye-affinity, impactresistance, machinability, etc. so that it is suitably used as materialsfor optical elements such as eyeglass lenses and camera lenses and asmaterials for glazing materials, coating materials and adhesives.

The lens made of the sulfur-containing urethane-based resin according tothe present invention may undergo physical and/or chemical treatmentssuch as surface polishing, antistatic treatment, hard coat treatment,anti-reflection coat treatment, coloring treatment and dimming treatmentin order to improve or impart such properties as anti-reflection, highhardness, abrasion resistance, chemical resistance, fog resistance andfashion-ability, as required.

The present invention will be described in more detail by reference tothe following Examples and Comparative Examples. In the performancetests of the lenses obtained, refractive index, Abbe's number,weatherability, optical distortion, impact resistance, heat resistanceand dye-affinity are evaluated in accordance with the following testingmethods.

Refractive index and Abbe's number: Measured at 20° C. by means of aPulfrich refractometer.

Weatherability: A sample of the resin was laid on a Weatherometerequipped with a sunshine carbon arc lamp. After a lapse of 200 hours,the resin was taken out and its hue was compared with the hue of theresin prior to the test. The criterion of evaluation was as follows: nochange - - - (O); slightly yellowing - - - (Δ); and yellowing - - - (X).

Optical distortion: Determined visually means of a strain inspector: nooptical distortion observed - - - (O); and optical distortionobserved - - - (X).

Impact resistance: Measured in accordance with FDA a standard bydropping an iron ball of 16.3 g from a height of 127 cm: notbroken - - - (O); cracked - - - (Δ); and broken - - - (X).

Heat resistance: Measured by the TMA method: resistant above 100°C. - - - (O); resistant at 90-100° C. - - - (Δ); and resistant below 90°C. - - - (X).

Dye-affinity: A resin specimen was immersed in a water dispersioncontaining 0.5% by weight of a disperse dye (MLP Blue-2 manufactured byMitsui Toatsu Dye Ltd.) under stirring. After 10 minutes, the specimenwas taken out and washed: dyed - - - (O); and not dyed - - - (X).

EXAMPLE 1

To a mixed solution of 78.1 g (1.0 mole) of 2-mercaptoethanol and 2.0 gof triethylamine were added 92.5 g (1.0 mole) of epichlorohydrindropwise over an hour while maintaining the temperature at 35-45° C.,followed by maturing at 40° C. for an hour.

An aqueous solution, formed in advance by dissolving 125.0 g (0.5 mole)of Na₂ S·9H₂ O in 100 g of pure water, was added dropwise to thereaction liquid over an hour while maintaining the temperature at 40-45°C., followed by maturing at 45° C. for an hour, thereby obtaining thefollowing tetrafunctional compound corresponding to formula (4).Identification was made by means of NMR. ##STR19##

Then, 303.8 g (3.0 moles) of 36% hydrochloric acid and 190.3 g (2.5moles) of thiourea were added to the reaction liquid and the mixture washeated at 110° C. for 9 hours under stirring.

The mixture was cooled to room temperature, to which were added 400 mlof toluene and then slowly 306.5 g (4.5 moles) of 25% aqueous ammonia,followed by hydrolysis at 60° C. for 3 hours.

The organic layer thus obtained was washed in sequence with 100 ml of36% hydrochloric acid, 100 ml of water, 100 ml of dilute aqueousammonia, and 100 ml of water twice. The toluene was distilled off by arotary evaporator and dust was separated by suction filtration to obtain174.6 g (0.476 mole; yield 95.2%) of the below-described polythiol FSH4as a colorless and transparent liquid. ##STR20##

These isomers were each isolated by reversed-phase chromatography tosubject them to identification.

The results of elemental analysis, IR, MS and NMR of FSH4-(A) component##STR21## are shown below.

    ______________________________________                                        <Elemental analysis>                                                          ______________________________________                                                    Found (%) Calculated (%)                                          ______________________________________                                          C 32.7 32.8                                                                   H  6.2  6.1                                                                   S 61.1 61.2                                                                 ______________________________________                                                   <IR ν.sub.max (KBr) cm.sup.-1 >                                     2543 (SH)                                                                   <MS>                                                                            m/z = 366 (M.sup.+)                                                         <.sup.13 C-NMR CDCl.sub.3 >                                                 ______________________________________                                                                 δ ppm                                          ______________________________________                                                                   a.sub.1 = 24.9  a.sub.2 = 35.1  a.sub.3 = 28.5                               a.sub.4 = 48.7  a.sub.5 = 35.9                      ______________________________________                                    

Then, the results for FSH4-(C) component ##STR23## is shown below.

The results of elemental analysis, IR and MS were the same as those forthe component (A).

    ______________________________________                                        <.sup.13 C-NMR CDCl.sub.3 >                                                                           δ ppm                                           ______________________________________                                                                  cSTR24##                                                                    .sub.1 = 24.7  c.sub.2 = 35.5  c.sub.3 = 36.8                                 c.sub.4 = 49.4  c.sub.5 = 28.6                        ______________________________________                                    

Finally, the results for FSH4-(B) component ##STR25## is shown below.

The results of elemental analysis, IR and MS were the same as those forthe component (A).

    ______________________________________                                        <.sup.13 C-NMR CDCl.sub.3 >                                                                          δ ppm                                            ______________________________________                                                                          bSTR26##                                                                    .sub.1 = 24.9  b.sub.2 = 35.1  b.sub.3 =                                      28.5  b.sub.4 = 48.7  b.sub.5 = 35.9                                          b.sub.6 = 28.6  b.sub.6 = 49.4  b.sub.6 =                                     36.8  b.sub.6 = 35.5  b.sub.10 = 24.7         ______________________________________                                    

EXAMPLE 2

To a mixed solution of 108.2 g (1.0 mole) of thioglycerol and 4.0 g oftriethylamine were added 92.5 g (1.0 mole) of epichlorohydrin dropwiseover an hour while maintaining the temperature at 45-50° C., followed bymaturing at 50° C. for 0.5 hour, thereby obtaining the below-describedtetrafunctional compound corresponding to formula (4). Identificationwas made similarly to Example 1 by means of NMR. ##STR27##

Then, 400.0 g (3.36 moles) of thionyl chloride were added dropwise tothe reaction liquid over an hour at a temperature of 50° C., followed bymaturing at 60° C. for 7 hours. The resulting liquid was cooled to roomtemperature, to which 100 g of pure water were added dropwise todecompose excess thionyl chloride. EDC in an amount of 300 g was addedthereto to extract the chlorinated product.

The EDC layer was washed twice with 100 g of pure water and the EDC wasdistilled off under vacuum by a rotary evaporator to obtain 247.8 g(0.968 mole) of the following chlorinated derivatives corresponding toformula (4). Identification was made similarly by means of NMR.##STR28##

Then, 368.4 g (4.84 moles) of thiourea and 500 g of pure water wereadded to the chlorinated derivatives, and the mixture was heated at 105°C. for an hour under stirring. The mixture was cooled to roomtemperature, to which were added 1.5 1 of toluene and then slowly 500.0g (8.92 moles) of hydrazine hydrate to hydrolyze the reaction product at80° C. for an hour.

The organic layer thus obtained was subjected to purification andremoval in the same manner as in Example 1 to obtain 225.9 g (0.917mole; yield 91.7%) of the following polythiol FSH1 as a colorless,transparent and viscous liquid. ##STR29##

The results of elemental analysis, IR, MS and NMR are shown below.

    ______________________________________                                        <Elemental analysis>                                                          ______________________________________                                                    Found (%) Calculated (%)                                          ______________________________________                                          C 30.7 29.2                                                                   H  5.8  5.7                                                                   S 64.5 65.0                                                                 ______________________________________                                                   <IR ν.sub.max (KBr) cm.sup.-1 >                                     2544 (SH)                                                                   <MS>                                                                            m/z = 246(M.sup.+)                                                          <.sup.13 C-NMR CDCl.sub.3 >                                                 ______________________________________                                                            δ ppm                                               ______________________________________                                                              a = 27.9  b = 50.3                                      ______________________________________                                    

EXAMPLE 3

To a liquid mixture of 78.1 g of 2-mercaptoethanol and 1.0 g oftriethylamine were added 43.0 g (0.5 mole) of 1,2,3,4-butadienediepoxidedropwise over an hour at a temperature of 35-40° C., followed bymaturing at 40° C. for an hour to obtain a colorless, transparent andviscous liquid. The liquid was identified as the followingtetrafunctional compound corresponding to formula (6) from the data ofNMR. ##STR31##

Then, 303.9 g (3.0 moles) of 36% hydrochloric acid and 190.3 g (2.5moles) of thiourea were added to the reaction liquid, and the mixturewas heated at 110° C. for 3 hours under stirring to carry out thereaction. The reaction mixture was cooled to room temperature, to whichwere added 300 ml of toluene and then slowly 272.4 g (4.0 moles) of 25%aqueous ammonia, followed by hydrolysis at 55-65° C. for 3 hours.

The organic layer was separated and then subjected to purification andremoval in the same manner as in Example 1 to obtain 145.6 g (0.475mole; yield 95.0%) of the following polythiol FSH2 as a colorless,transparent and viscous liquid. ##STR32##

The results of elemental analysis, IR, MS and NMR are shown below.

    ______________________________________                                        <Elemental analysis>                                                          ______________________________________                                                    Found (%) Calculated (%)                                          ______________________________________                                          C 31.3 31.3                                                                   H  5.9  5.9                                                                   S 62.6 62.7                                                                 ______________________________________                                                   <IR ν.sub.max (KBr) cm.sup.-1 >                                     2544 (SH)                                                                   <MS>                                                                            m/z = 306(M.sup.+)                                                          <.sup.13 C-NMR CDCl.sub.3 >                                                 ______________________________________                                                          δ ppm                                                 ______________________________________                                                            a = 28.6  b = 48.7  c = 35.5  d = 24.7                    ______________________________________                                    

EXAMPLE 4

To a liquid mixture of 78.1 g (1.0 mole) of 2-mercaptoethanol, 186.9 g(0.5 mole) of 1,2,3,4-tetrabromobutane and 500 ml of ethanol were added81.6 g (1.0 mole) of 49% NaOH dropwise over 2 hours at a temperature of40-60° C., followed by maturing at 50° C. for 2 hours. After completionof the reaction, the reaction mixture was cooled to room temperature andthe NaBr thereby deposited was separated by filtration. The ethanol andwater were distilled off the filtrate by an evaporator to obtain acolorless and viscous liquid. The liquid was identified as the followingtetrafunctional compound corresponding to formula (6) from the data ofNMR. ##STR34##

Then, 257.9 g (1.5 moles) of 47' hydrobromic acid and 190.3 g (2.5moles) of thiourea were added to the viscous liquid. The mixture wassubjected to isothiouronium salt reaction, hydrolysis, purification andremoval in the same manner as in Example 3 to obtain 131.7 g (0.429mole; yield 85.8%) of the following polythiol FSH2, the same polythiolas obtained in Example 3, as a colorless, transparent and viscousliquid. ##STR35##

EXAMPLE 5

To a liquid mixture of 156.2 g (2.0 moles) of 2-mercaptoethanol, 186.9 g(0.5 mole) of 1,2,3,4-tetrabromobutane and 500 ml of DMF were added163.2 g (2.0 moles) of 49% NaOH dropwise over 2 hours at a temperatureof 40-60° C., followed by maturing at 100° C. for 5 hours. Aftercompletion of the reaction, the reaction mixture was cooled to roomtemperature and the NaBr thereby deposited was separated by filtration.The DMF and water were distilled off the filtrate by an evaporator toobtain a colorless and viscous liquid. The liquid was identified as thefollowing tetrafunctional compound corresponding to formula (6) from thedata of NMR. ##STR36##

Then, 253.2 g (2.5 moles) of 36% hydrochloric acid and 152.2 g (2.0moles) of thiourea were added to the viscous liquid. The mixture wassubjected to isothiouronium salt reaction, hydrolysis, purification andremoval in the same manner as in Example 3 to obtain 205.0 g (0.480mole; yield 96.0%) of the following polythiol FSH5, as a colorless,transparent and viscous liquid. ##STR37##

The results of elemental analysis, IR, MS and NMR are shown below.

    ______________________________________                                        <Elemental analysis>                                                          ______________________________________                                                    Found (%) Calculated (%)                                          ______________________________________                                          C 33.6 33.8                                                                   H  6.0  6.1                                                                   S 60.3 60.1                                                                 ______________________________________                                                   <IR ν.sub.max (KBr) cm.sup.-1 >                                     2544 (SH)                                                                   <MS>                                                                            m/z = 426(M.sup.+)                                                          <.sup.13 C-NMR CDCl.sub.3 >                                                 ______________________________________                                                          δ ppm                                                 ______________________________________                                                            a = 26.9  b = 48.8  c = 35.1  d = 24.9  e = 24.7  f =                       35.5                                                        ______________________________________                                    

EXAMPLE 6

To a KOH solution, formed by dissolving 26.5 g (0.40 mole) of 85% KOHflake in 200 ml of isopropyl alcohol, were added dropwise 31.6 g (0.40mole) of 2-mercaptoethanol at room temperature to carry outsalt-forming.

Then, a solution, formed in advance by dissolving 52.4 g (0.20 mole) ofpentaerythritol-dibromide-[2,2-bis(bromomethyl)-1,3-propanediol] in 170ml of isopropyl alcohol, was added dropwise to the salt mass over anhour at a temperature of 70° C., followed by maturing at 70° C. for 3hours. After completion of the reaction, the reaction mixture was cooledto room temperature, and the NaBr thereby deposited was separated byfiltration. The isopropyl alcohol and water were distilled off thefiltrate by an evaporator to obtain a colorless and viscous liquid. Theliquid was identified as the following tetrafunctional compoundcorresponding to formula (5) from the data of NMR. ##STR39##

After 108.3 g (0.40 mole) of PBr₃ had been added dropwise to the viscousliquid at 50° C., the reaction was continued at 100° C. for 10 hours.After completion of the reaction, the reaction mixture was cooled toroom temperature, to which were added 50 ml of pure water dropwise andthen 200 ml of toluene to extract an organic layer.

The organic layer thus obtained was washed with 100 ml of an aqueous 1%NaHCO₃ solution once and then with 100 ml of pure water twice. Thetoluene was distilled off the organic layer by a rotary evaporator.

The remaining residue was identified as the following tetrafunctionalcompound corresponding to formula (5). ##STR40##

Subsequently, 112.2 g (2.00 moles) of NaSH were dissolved in 700 ml ofDMF, to which 163.2 g (2.00 moles) of 49% NaOH were added slowly. Aftercooling the mixture to 30° C., 152.2 g (2.00 moles) of CS₂ were addedthereto dropwise to carry out maturing at 40° C. for 2 hours.Thereafter, the foregoing brominated derivative dissolved in 200 ml ofDMF was added slowly to the matured mixture to carry out the reaction at100° C. for 2 hours.

The reaction liquid was cooled to room temperature, to which 300.0 g(2.96 moles) of 36% hydrochloric acid were added to hydrolyze thereaction product at 30° C. for an hour. The resultant reaction liquidwas heated to 55° C. to recover the CS₂, and then cooled to roomtemperature. Subsequently, 800 ml of chloroform and 2,000 ml of waterwere added thereto to extract the product and the organic layer wasseparated. The organic layer was neutralized with 1% aqueous ammonia andwashed with 500 ml of pure water three times. The chloroform was thenremoved by vacuum distillation.

The residue was added to a liquid mixture of 500 ml of toluene and 2,000ml of ethanol, to which 10 g of zinc powder were added. To the resultantmixture were added 120 g (1.19 moles) of 36% hydrochloric acid dropwisewhile maintaining the temperature at 30° C. and then 500 g of pure waterto extract the organic layer. The organic layer was washed with 300 mlof pure water three times, and the toluene was distilled off undervacuum to obtain 57.0 g (0.178 moles; yield 89.0%) of the followingpolythiol FSH3. ##STR41##

The results of elemental analysis, IR, MS and NMR are shown below.

    ______________________________________                                        <Elemental analysis>                                                          ______________________________________                                                    Found (%) Calculated (%)                                          ______________________________________                                          C 33.7 33.7                                                                   H  6.3  6.3                                                                   S 59.9 60.0                                                                 ______________________________________                                                   <IR ν.sub.max (KBr) cm.sup.-1 >                                     2544 (SH)                                                                   <MS>                                                                            m/z = 320(M.sup.+)                                                          <.sup.13 C-NMR CDCl.sub.3 >                                                 ______________________________________                                                              δ ppm                                             ______________________________________                                                                a = 24.9  b = 35.1  c = 36.9  d = 14.6  e =           ______________________________________                                                              28.4                                                

EXAMPLE 7

The following polythiol FSH6 was obtained in the same manner as inExample 6, except that the amounts of KOH flake and 2-mercaptoethanolwere reduced to half of those used in Example 6. ##STR43##

The results of elemental anaylsis, IR, MS and NMR are shown below.

    ______________________________________                                        <Elemental analysis>                                                          ______________________________________                                                    Found (%) Calculated (%)                                          ______________________________________                                          C 32.5 32.3                                                                   H  6.3  6.2                                                                   S 61.1 61.5                                                                 ______________________________________                                                   <IR ν.sub.max (KBr) cm.sup.-1 >                                     2544 (SH)                                                                   <MS>                                                                            m/z = 260(M.sup.+)                                                          <.sup.13 C-NMR CDCl.sub.3 >                                                 ______________________________________                                                           δ ppm                                                ______________________________________                                                             a = 24.9  b = 35.1  c = 36.9  d = 47.6  e = 28.4         ______________________________________                                    

EXAMPLE 8

Salt-forming was carried out in the same manner as in Example 6 byadding 71.1 g (0.60 mole) of 2-mercaptoethanol to a KOH solution formedby dissolving 39.8 g (0.60 mole) of 85% KOH flake in 300 ml of isopropylalcohol. The salt mass thus formed was reacted with 77.5 g (0.20 mole)of pentaerythritol tetrabromide in the same manner as in Example 6 toobtain the following tetrafunctional compound. Identification was madeby means of NMR. ##STR45##

The compound was thiolated by the use of the isothiouronium salt processin the same manner as in Example 1 to obtain the following polythiolFSH7. ##STR46##

The results of elemental analysis, IR, MS and NMR are shown below.

    ______________________________________                                        <Elemental analysis>                                                          ______________________________________                                                    Found (%) Calculated (%)                                          ______________________________________                                          C 34.7 34.7                                                                   H  6.3  6.4                                                                   S 58.8 58.9                                                                 ______________________________________                                                   <IR ν.sub.max (KBr) cm.sup.-1 >                                     2544 (SH)                                                                   <MS>                                                                            m/z = 380(M.sup.+)                                                          <.sup.13 C-NMR CDCl.sub.3 >                                                 ______________________________________                                                         δ ppm                                                  ______________________________________                                                           a = 24.9  b = 35.1  c = 36.9  d = 47.6  e = 28.4           ______________________________________                                    

EXAMPLE 9

The following compound was obtained in the same manner as in Example 3except that the amount of 2-mercaptoethanol was reduced to half.Identification was made by means of NMR. ##STR48##

The following polythiol FSH8 was obtained by bromination and thiolationin the same manner as in Example 6. ##STR49##

The results of elemental analysis, IR, MS and NMR are shown below.

    ______________________________________                                        <Elemental analysis>                                                          ______________________________________                                                    Found (%) Calculated (%)                                          ______________________________________                                          C 29.2 29.2                                                                   H  5.7  5.7                                                                   S 65.0 65.0                                                                 ______________________________________                                                   <IR ν.sub.max (KBr) cm.sup.-1 >                                     2544 (SH)                                                                   <MS>                                                                            m/z = 246(M.sup.+)                                                          <.sup.13 C-NMR CDCl.sub.3 >                                                 ______________________________________                                                          δ ppm                                                 ______________________________________                                                            a = 24.9  b = 35.1  c = 28.5  d = 48.7  e = 40.4  f                         =28.4                                                       ______________________________________                                    

EXAMPLE 10

To a liquid mixture of 39.1 g (0.50 mole) of 2-mercaptoethanol and 1.0 gof triethylamine were added dropwise 46.3 g (0.50 mole) ofepichlorohydrin at a temperature of 35-40° C., followed by maturing at40° C. for an hour.

After introducing 54.1 g (0.50 mole) of 1-thioglycerol into the reactionliquid, 40.8 g (0.50 mole) of 49% NaOH were added thereto dropwise at atemperature of 35-40° C., and the resultant reaction liquid was maturedat 40° C. for an hour to obtain the following tetrafuctional compound.Identification was made by means of NMR. ##STR51##

Then, the compound was brominated in the same manner as in Example 6 andthiolated in the same manner as in Example 2, thereby obtaining thefollowing polythiol FSH9. ##STR52##

The results of elemental analysis, IR, MS and NMR are shown below.

    ______________________________________                                        <Elemental analysis>                                                          ______________________________________                                                    Found (%) Calculated (%)                                          ______________________________________                                          C 31.2 31.1                                                                   H  5.9  5.9                                                                   S 62.8 63.0                                                                 ______________________________________                                                   <IR ν.sub.max (KBr) cm.sup.-1 >                                     2544 (SH)                                                                   <MS>                                                                            m/z = 306(M.sup.+)                                                          <.sup.13 C-NMR CDCl.sub.3 >                                                 ______________________________________                                                              δ ppm                                             ______________________________________                                                                a = 27.9  b = 50.3  c = 35.9  d = 48.7  e = 28.5                            f = 35.1  g = 24.9                                      ______________________________________                                    

EXAMPLE 11

To a liquid mixture comprising 128.0 g (0.50 mole) of the followingchlorinated derivatives obtained in Example 2: ##STR54## and 156.2 g(2.00 moles) of 2-mercaptoethanol were added dropwise 163.3 g (2.00moles) of 49% NaOH at 35-40° C., followed by maturing at 50° C. for 2hours, thereby obtaining the following polyols. Identification was madeby means of NMR. ##STR55##

These polyols were thiolated in the same manner as in Example 1 toobtain the following polythiol FSH10. ##STR56##

The results of elemental analysis, IR, MS and NMR are shown below.

    ______________________________________                                        <Elemental analysis>                                                          ______________________________________                                                    Found (%) Calculated (%)                                          ______________________________________                                          C 34.2 34.3                                                                   H  6.2  6.2                                                                   S 59.2 59.3                                                                 ______________________________________                                                   <IR ν.sub.max (KBr) cm.sup.-1 >                                     2544 (SH)                                                                   <MS>                                                                            m/z = 486 (M.sup.+)                                                         <.sup.13 C-NMR CDCl.sub.3 >                                                 ______________________________________                                                                  δ ppm                                         ______________________________________                                                                    a = 24.7  b = 35.5  c = 36.8  d = 49.4            ______________________________________                                    

EXAMPLE 12

In the same manner as in Example 3, 39.1 g (0.50 mole) of2-mercaptoethanol were reacted with 43.0 g (0.50 mole) of1,2,3,4-butadienediepoxide. The reaction product was further reactedwith 54.1 g (0.50 mole) of 1-thioglycerol to obtain the followingpolyol. ##STR58##

The polyol was chlorinated, polythiolated and purified by the procedureof Example 2 to obtain the following polythiol FSH11. ##STR59##

The results of elemental analysis, IR, MS and NMR are shown below.

    ______________________________________                                        <Elemental analysis>                                                          ______________________________________                                                    Found (%) Calculated (%)                                          ______________________________________                                          C 30.6 30.6                                                                   H  5.7  5.7                                                                   S 63.4 63.6                                                                 ______________________________________                                                   <IR ν.sub.max (KBr) cm.sup.-1 >                                     2544 (SH)                                                                   <MS>                                                                            m/z = 352 (M.sup.+)                                                         <.sup.13 C-NMR CDCl.sub.3 >                                                 ______________________________________                                                                 δ ppm                                          ______________________________________                                                                   a = 24.9  b = 35.5  c = 28.6  d = 24.7  e =                                 49.5  f = 28.7  g = 50.4  h = 28.0                   ______________________________________                                    

EXAMPLE 13

The following isomer mixture polythiol FSH4 synthesized in Example 1##STR61## in an amount of 36.7 g (0.10 mole) was mixed uniformly with37.6 g (0.20 mole) of m-xylylenediisocyanate (hereinafter referred to asXDi). The mixture was charged into a mold consisting of a glass mold anda gasket made of a thermoplastic elastomer manufactured by MitsuiPetrochemical Industries, Ltd., where the mixture was cured by heatingat 20-120° C. for 12 hours.

The sulfur-containing urethane-based plastic lens thus obtained wascolorless and transparent and had entirely no cloudiness at theperiphery due to the bleeding from the gasket. The properties of thelens are illustrated in Table 1. The IR chart of the resin obtained isshown in FIG. 1.

COMPARATIVE EXAMPLE 1

A sulfur-containing urethane-based lens was obtained by resinifying 41.7g (0.16 mole) of GST (1,2-bis(mercaptoethylthio)-3-propanethiol) and45.2 g (0.24 mole) of XDi under conditions of Example 13.

The center part of the lens was colorless and transparent and had noproblems, but cloudiness was observed at the periphery due to thebleeding from the gasket.

The properties of the lens thus obtained are given in Table 2.

COMPARATIVE EXAMPLE 2

A sulfur-containing urethane-based lens was obtained by forming a resinfrom 32.1 g (0.16 mole) of GMT(1,2-bis(mercaptoethylthio)-1,3-propanedithiol) and 45.2 g (0.24 mole)of XDi under conditions of Example 13.

As a result, cloudiness was observed at the periphery due to thebleeding from the gasket, similarly to Comparative Example 1. Theproperties of the lens thus obtained are given in Table 2.

COMPARATIVE EXAMPLE 3

A sulfur-containing urethane-based lens was obtained by forming a resinfrom 34.6 g (0.17 mole) of PET (tetrakis(mercaptomethyl)methane) and65.4 g (0.34 mole) of XDi under conditions of Example 13.

The lens had no cloudiness at the periphery due to the bleeding from thegasket and was colorless and transparent as a whole. However, it couldhardly be dyed.

The properties of the lens thus obtained are given in Table 2.

COMPARATIVE EXAMPLE 4

A sulfur-containing urethane-based lens was obtained by forming a resinfrom 30.5 g (0.15 mole) of PET, 122.4 g (0.47 mole) of GST and 188.2 g(1.00 mole) of XDi under conditions of Example 13.

As a result, cloudiness was observed at the periphery due to thebleeding from the gasket, similarly to Comparative Example 1. Theproperties of the lens thus obtained are given in Table 2.

EXAMPLES 14-47 AND COMPARATIVE EXAMPLES 5-10

Sulfur-containing urethane-based plastic lenses were produced in thesame manner as in Example 13. The results are shown in Tables 1 and 2.All the lenses obtained in the Examples were colorless and transparentand had entirely no cloudiness at the periphery due to bleeding from thegasket.

                                      TABLE 1                                     __________________________________________________________________________         Novel                                                                              Isocya-        Refrac-     Heat                                                                             Dye                                                                              Impact   Optical                      Polythiol nate Modifier tive Abbe's Specific resis- af- resis-                                                                 Weather- dis-                                                                  Example (mol) (mol)                                                          (mol) index number                                                            gravity tance finity                                                          tance ability             __________________________________________________________________________                                                        tortion                     13 FSH4  XDi   1.66  32  1.37  ∘  ∘  .smallcircl                                                        e.  ∘                                                             ∘                                                                   mixture (0.20)                                                                (0.10)                    14 FSH4 (A) XDi  1.66 32 1.37 ∘ ∘ ∘                                                         ∘                                                                 ∘                                                                   (0.10) (0.20)                                                                15 FSH4 (B) XDi                                                              1.66 32 1.37 .smallcir                                                        cle. ∘                                                            ∘                                                                 ∘                                                                 ∘                                                                   (0.10) (0.20)                                                                16 FSH4 (C) XDi                                                              1.66 32 1.37 .smallcir                                                        cle. ∘                                                            ∘                                                                 ∘                                                                 ∘                                                                   (0.10) (0.20)                                                                17 FSH1 XDi GST 1.66                                                         32 1.36 ∘                                                         ∘                                                                 ∘                                                                 ∘                                                                 ∘                                                                   (0.07) (0.20)                                                               (0.04)                      18 FSH2 XDi  1.66 32 1.36 ∘ ∘ ∘                                                             ∘                                                                 ∘                                                                   (0.10) (0.20)                                                                19 FSH3 XDi  1.66 32                                                         1.36 ∘                                                            ∘                                                                 ∘                                                                 ∘                                                                 ∘                                                                   (0.10) (0.20)                                                                20 FSH6 XDi GST 1.66                                                         32 1.36 ∘                                                         ∘                                                                 ∘                                                                 ∘                                                                 ∘                                                                   (0.07) (0.20)                                                               (0.04)                      21 FSH8 XDi GST 1.66 32 1.35 ∘ ∘ ∘                                                          ∘                                                                 ∘                                                                   (0.07) (0.20)                                                               (0.04)                      22 FSH9 XDi GST 1.66 32 1.36 ∘ ∘ ∘                                                          ∘                                                                 ∘                                                                   (0.078) (0.20)                                                              (0.03)                      23 FSH11 XDi GST 1.66 32 1.35 ∘ ∘ ∘                                                         ∘                                                                 ∘                                                                   (0.07) (0.20)                                                               (0.04)                      24 FSH1 BIMD  1.70 31 1.54 ∘ ∘ ∘                                                            ∘                                                                 ∘                                                                   (0.10) (0.20)                                                                25 FSH2 BIMD  1.70                                                           31 1.53 ∘                                                         ∘                                                                 ∘                                                                 ∘                                                                 ∘                                                                   (0.10) (0.20)                                                                26 FSH6 BIMD  1.70                                                           31 1.54 ∘                                                         ∘                                                                 ∘                                                                 ∘                                                                 ∘                                                                   (0.10) (0.20)                                                                27 FSH8 BIMD  1.70                                                           31 1.53 ∘                                                         ∘                                                                 ∘                                                                 ∘                                                                 ∘                                                                   (0.10) (0.20)                                                                28 FSH9 BIMD  1.70                                                           31 1.54 ∘                                                         ∘                                                                 ∘                                                                 ∘                                                                 ∘                                                                   (0.10) (0.20)                                                                29 FSH11 BIMD  1.70                                                          31 1.53 ∘                                                         ∘                                                                 ∘                                                                 ∘                                                                 ∘                                                                   (0.10) (0.20)                                                                30 FSH1 XDi  1.60 40                                                         1.28 ∘                                                            ∘                                                                 ∘                                                                 ∘                                                                 ∘                                                                   (0.10) (0.20)                                                                31 FSH2 HMDi (0.10)                                                          1.60 41 1.22 .smallcir                                                        cle. ∘                                                            ∘                                                                 ∘                                                                 ∘                                                                   (0.10) TMDi (0.10)                                                           32 FSH3 HMDi (0.10)                                                          1.60 41 1.23 .smallcir                                                        cle. ∘                                                            ∘                                                                 ∘                                                                 ∘                                                                   (0.10) TMDi (0.10)                                                           33 FSH4 HMDi (0.10)                                                          1.60 41 1.25 .smallcir                                                        cle. ∘                                                            ∘                                                                 ∘                                                                 ∘                                                                   (0.10) TMDi (0.10)                                                           34 FSH5 HMDi  1.60                                                           42 1.24 ∘                                                         ∘                                                                 ∘                                                                 ∘                                                                 ∘                                                                   (0.10) (0.20)                                                                35 FSH7 HMDi (0.10)                                                          1.60 42 1.24 .smallcir                                                        cle. ∘                                                            ∘                                                                 ∘                                                                 ∘                                                                   (0.10) TMDi (0.10)                                                           36 FSH10 HMDi  1.60                                                          42 1.24 ∘                                                         ∘                                                                 ∘                                                                 ∘                                                                 ∘                                                                   (0.10) (0.20)                                                                37 FSH4 H6XDi  1.60                                                          41 1.30 ∘                                                         ∘                                                                 ∘                                                                 ∘                                                                 ∘                                                                   (0.10) (0.20)                                                                38 FSH4 NBDi  1.62                                                           40 1.30 ∘                                                         ∘                                                                 ∘                                                                 ∘                                                                 ∘                                                                   (0.10) (0.20)                                                                39 FSH4 IPDi (0.10)                                                          1.60 40 1.26 .smallcir                                                        cle. ∘                                                            ∘                                                                 ∘                                                                 ∘                                                                   (0.10) HDi (0.10)                                                            40 FSH4 XDi PET 1.66                                                         32 1.38 ∘                                                         ∘                                                                 ∘                                                                 ∘                                                                 ∘                                                                   (0.10) (0.30)                                                               (0.05)                      41 FSH4 HMDi PEMP 1.60 42 1.24 ∘ ∘ ∘                                                         ∘                                                                ∘                                                                   (0.10) (0.22)                                                               (0.01)                      42 FSH4 HMDi Cyclo- 1.60 42 1.23 ∘ ∘ .smallcircl                                                        e. ∘                                                              ∘                                                                   (0.10) (0.18) hexyl          isocyanate                                                                    (0.04)                                                                     43 FSH4 XDi 1-Thio- 1.65 33 1.36 ∘ ∘ .smallcircl                                                        e. ∘                                                              ∘                                                                   (0.10) (0.23)                                                               glycerin                       (0.02)                                                                     44 FSH4 XDi 1,4- 1.66 32 1.36 ∘ ∘ ∘                                                         ∘                                                                 ∘                                                                   (0.10) (0.25)                                                               Dithian-                       2,5-di                                                                        mercapto-                                                                     methyl                                                                        (0.05)                                                                     45 FSH4 Bis(4-isothio-  1.75 20 1.38 ∘ ∘                                                                ∘                                                                 ∘                                                                 ∘                                                                   (0.10) cyanatophenyl                                                        )                             sulfide (0.15)                                                                XDi (0.05)                                                                  46 FSH4 OCNCH.sub.2 SSCH.sub.2 NCS  1.75 23 1.58 ∘ .smallcir                                                        cle. ∘                                                            ∘                                                                 ∘                                                                   (0.10) (0.20)                                                                47 FSH4 XDi (0.19)                                                           1.66 33 1.36 .smallcir                                                        cle. ∘                                                            ∘                                                                 ∘                                                                 ∘                                                                   (0.10) IPDi             __________________________________________________________________________                                                        (0.09)                

                                      TABLE 2                                     __________________________________________________________________________    Comparative                                                                         Polythiol   Isocyanate                                                                         Refractive                                                                          Abbe's                                                                            Specific                                                                           Heat Dye Impact                                                                              Weather-                                                                           Optical                                                                        Example (mol)                                                                (mol) index                                                                   number gravity                                                                resistance                                                                    affinity                                                                      resistance                                                                    ability                                                                       distortion          __________________________________________________________________________    1     GST         XDi  1.66  32  1.35 Δ                                                                            ◯                                                                     ◯                                                                       ◯                                                                      ◯                                                                   (0.16) (0.24)       2 GMT  XDi 1.66   32 1.34 ◯ ◯ ◯                                                                   ◯                                                                 ◯                                                                   (0.16) (0.24)       3 PET XDi 1.66 32 1.38  ◯ X ◯ ◯                                                                   ◯                                                                   (0.7)  (0.34)       4 PET (0.15) XDi 1.66 32 1.36 ◯ ◯ ◯                                                               ◯                                                                 ◯                                                                   GST (0.47)                                                                  (1.00)                5 Pentaerythritoltetrakis- XDi 1.60 35  1.44 ◯ ◯                                                               ◯                                                                ◯                                                                 ◯                                                                   thioglycolate                                                               (0.10) (0.20)                                                                  6 Tetrabromobis                                                              phenol A XDi                                                                  1.61 31 1.52                                                                  ◯ X                                                               X X X                  (0.20) (0.20)                                                                7 1,4-Benzenedithiol XDi 1.68 28 1.36 ◯ X X Δ                                                                       ◯                                                                   (0.20) (0.25)        - 8                                                                                                                                    XDi  (0.20)                                                                 1.66 30 1.34                                                                  ◯                                                                 ◯ X                                                               Δ                                                                       ◯                                                                   - 9                                                                           XDi  (0.18)                                                                 1.64 31 1.26 X                                                                ◯                                                                 ◯                                                                 ◯                                                                 ◯                                                                   - 10                                                                        1,4-Dithian-2,5-                                                              dimer- XDi 1.66                                                               32 1.38                                                                       ◯ X                                                               X ◯                                                               ◯                                                                   captomethyl                                                                 (0.20) (0.20)       __________________________________________________________________________     ##STR64##

What is claimed is:
 1. A sulfur-containing urethane-based resincomposition comprising a polythiol having four or more functional groupsand at least one isocyanate selected from the group consisting ofpolyisocyanate compounds, polyisothiocyanate compounds and isocyanatogroup-containing polyisothiocyanate compounds, said polythiol beingrepresented by any of the following formula (1): wherein R1, R2, R3 andR4 are each selected from the group consisting of H, --CH₂ SH, --CH₂SCH₂ CH₂ SH, ##STR65## provided that where any one of R1, R2, R3 and R4is H, at least one of the other three radicals represents ##STR66##where any two of R1, R2, R3 and R4 are H, two others are independentlyselected from ##STR67## and any three or all of R1, R2, R3 and R4 arenot H simultaneously; formula (2):

    (HSCH.sub.2).sub.4-m C(CH.sub.2 SCH.sub.2 CH.sub.2 SH).sub.m( 2)

wherein m denotes an integer of 1 to 3; and formula (3): ##STR68##wherein n denotes an integer of 0 to
 3. 2. The composition of claim 1wherein the proportion of the isocyanate to the polythiol is from 0.5 to3.0 in terms of the molar ratio of the functional groups (NCO+NCS)/SH.3. The process for producing a sulfur-containing urethane-based resin,which comprises curing the composition of claim 1 by heating.
 4. Asulfur-containing urethane-based resin obtained by the process of claim3.
 5. The process of claim 3 wherein the proportion of the isocyanate tothe isocyanate to the polythiol is from 0.5 to 3.0 in terms of the molarratio of the functional groups (NCO+NCS)/SH.
 6. A sulfur-containingurethane-based resin obtained by the process of claim
 5. 7. Thecomposition of claim 1 wherein the polythiol has the following formula:##STR69##
 8. The composition of claim 1 wherein the polythiol has thefollowing formula:
 9. The composition of claim 1 wherein the polythiolhas the following formula:
 10. The composition of claim 1 wherein thepolythiol has the following formula:
 11. The composition of claim 1wherein the polythiol has the following formula:
 12. The composition ofclaim 1 wherein the polythiol has the following formula:
 13. Thecomposition of claim 1 wherein the polythiol has the following formula:14. The composition of claim 1 wherein the polythiol has the followingformula:
 15. The composition of claim 1 wherein the polythiol has thefollowing formula:
 16. The composition of claim 1 wherein the polythiolhas the following formula:
 17. The composition of claim 1 wherein thepolythiol has the following formula:
 18. The composition of claim 1wherein the polythiol has the following formula:
 19. The composition ofclaim 1 wherein the polythiol has the following formula: